After getting back from a 3 day vacation, I was shocked to notice that my Betta has lost it's entire dorsal fin and losing more. I'm guessing its from Fin Rot but not sure. Will he make it?

Housing
What size is your tank? 30 gallon tank. QT into a 1 gal container atm.
What temperature is your tank? 70+
Does your tank have a filter? Yes
Does your tank have an air stone or other type of aeration? NoIs your tank heated? No
What tank mates does your betta fish live with? Bristle Nose Pleco

Food
What type of food do you feed your betta fish? Flakes and Pellet
How often do you feed your betta fish? Once everyday.

Maintenance
How often do you perform a water change? Once every 2 weeks
What percentage of the water do you change when you perform a water change? 25-50%
What type of additives do you add to the water when you perform a water change? Prime Water Conditioner

Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Nope

Symptoms and Treatment
How has your betta fish's appearance changed? Whole Dorsal Fin gone + more
How has your betta fish's behavior changed? Hasn't Eaten but swimming around actively
When did you start noticing the symptoms?After I got back from a 3 day vacation it was already to late
Have you started treating your fish? If so, how? Not yet, planning to get Aquarium Salt and Stress Coat tonight for my poor betta D:
Does your fish have any history of being ill? Was getting fin nipped by tetras but was separated soon after i noticed
How old is your fish (approximately)? 5 Months

Don't use AQ salt, this really isn't going to help a case like this. Stress Coat is great though!

I suggest going out to get Erythromycin at the pet store or....I hate to say it but BettaFix will help with this as well. Or KanaPlex. The addition of Vita-Chem will also help heal fins. Right now you want to stop all infection so I strongly suggest getting Erythromycin at least.

You're going to have to do 100% daily water changes so he doesn't get rot on his body, this is what's more than likely going to happen though. So we're going to try to prevent that. But I believe with 100% daily changes, get his temp up to 80 at least, 70 is too low. And dose with Erythromycin or one of the other things I mentioned along with using Stress Coat for your water conditioner.

Is there anyway you can heat the big tank up to 80 and then get a lighter tank that he can stay in and have that float in the big tank? I use critter keepers from wal-mart, 6 dollars for one that is roughly a gallon so it's easier to dose and scoop him out than a vase. That's what I'd do at least.

It is bad if you overdose, because it contains Tea Tree oil same as MelaFix, if you use too much it can coat the Betta's labyrinth organ and suffocate them. But if used in smaller dosages, he'll be fine. But for this boy, I really think you should start on some Erythromycin, Tetracycline or KanaPlex right away. You don't want the body to rot away either, it's very hard to cure after that.

If you can do once daily 100% water changes then great!!! If you can only do once every other day, that's fine too. But clean water is a must with him so, the best thing you can do is a daily 100% change